1. Field of the Invention
The present invention relates to an imaging apparatus, and in particular, to a smear correction technique for an imaging apparatus, such as a digital camera and a video camera, having a function for preventing degradation of image quality due to a smear phenomenon.
2. Description of the Related Art
When an image of a high-luminance object, such as the sun or a light, is photographed using an imaging apparatus having a charge coupled device (CCD) image sensor, a bright line in the form of a vertically extending stripe appears in the photographed image. Such a phenomenon is called a smear phenomenon, which is caused by leakage of a charge of a significant portion of incident light during transfer to a vertical transfer channel and subsequent read-out of charges created on the photodiodes (photoelectric conversion elements) of the CCD to the vertical transfer channel, or by leakage of the incident light itself to the vertical transfer channel, which creates a charge in the vertical transfer channel.
To eliminate such a smear phenomenon, in conventional imaging apparatuses, output signals from an optical black area (OB area) composed of a plurality of lines of the CCD image sensor are added and averaged to form one line's worth of signals, which are then stored in a line memory, and the stored signals are subtracted from a signal from an effective pixel area of the CCD image sensor (Japanese Patent Application Laid-Open No. 7-67038).